1. Field of the Invention
The present invention relates to electrical connectors for flexible boards.
2. Description of Related Art
Japanese patent application Kokai No. 142130/95 discloses an electrical connector of this type as shown in FIGS. 11-13. The spring contact sections 52A of contact elements 52 are disposed on an opening of a housing 51. The housing 51 has circular bearings on the opposite holding sections 53 for supporting a pressure member 54 for rotation (FIG. 11) between a closed position where the pressure member 54 is close to the contact elements 52 and an open position where the pressure member 54 is spaced from the closed position. The contact elements 52 are made by stamping a metal sheet so as to provide a fulcrum section 52B with their center aligned with the center of the circular bearings as shown in FIG. 12. The contact elements 52 are disposed in channels 51A of the housing 51 such that the fulcrum sections 52B form a comb-like cylindrical body or shaft between the circular bearings. The pressure member 54 has a concave bearing face 54A such that when the pressure member 54 rotates about the circular bearings, the bearing face 54a engages the comb-like shaft for rotation. The pressure member 54 has a pressure edge 54B for pressing a flexible board F against the spring contact sections 52A in the opening of the housing 51.
As shown in FIG. 12, the housing 51 has receiving faces 51B at a position deeper than the spring contact sections 52A for raising the leading edge of the flexible board F so that when the pressure member 54 is turned downwardly to the closed position, the pressure edge 54B of the pressure member 54 applies a pressure on the flexible board F between the spring contact sections 52A and the receiving faces 51b.
In operation, first of all, the pressure member 54 is turned upwardly to the open position as shown by phantom line in FIG. 12, and a flexible board F is put into the opening such that the connection conductors of the board F face down. At this point, the flexible board F is supported by the spring contact sections 52A and the receiving faces 51B. Then, the pressure member 54 is turned downwardly to the closed position as shown in FIG. 13, so that the pressure edge 54B depresses the flexible board F between the spring contact sections 52A and the receiving faces 52B. Thus, the connection conditions of the flexible board F are electrically connected under a predetermined pressure to the spring contact sections 52A of the contact elements 52.
When the pressure edge 54B abuts the flexible board F, the pressure member 54 receives a moment of a force and is pushed forwardly (to the left in the figure), but the fulcrum sections 52B engage the concave bearing face 54A to prevent the forward movement of the pressure member 54.
However, if the flexible board F is thicker than the expected, the operational force upon the pressure member 54 is larger, making the forward moving force larger. If the forward moving force is very large, the bearing face 54A can slip away from the fulcrum sections 52B. Especially, when the number of contact elements 52 is large so that the pressure member 54 is elongated, it is more likely to separate because of a flexure of the pressure member 54 between the circular bearings.